1. Field of the Invention
The present invention relates to a method and an apparatus for rolling tubes into tube plates, especially heat exchangers, with a tube roller that has expandable rollers.
2. Description of the Prior Art
With tube rollers, such as are known, for example, from U.S. Pat. No. 4,007,699--Clemens dated Feb. 15, 1977 as based on German Offenlegungsschrift No. 22 05 281 and German Offenlegungsschrift No. 23 31 341, the roll mandrel, which engages concentric rollers, is shifted in the direction toward the rollers until the required holding expansion is achieved. With the heretofore known methods, the holding expansion is measured as the torque that occurs at the drive motor, and when that set torque is achieved that corresponds to the desired holding expansion, at least the mandrel feed is switched off by the drive mechanism.
However, there was found that this indirect measurement of the holding expansion must be improved in order to achieve completely reproducible rolling results and even to avoid rerolling when the roll mandrel is in an axial state of rest.
An object of the present invention therefore is to provide a method and apparatus with which it is possible to more precisely detect when the desired holding expansion has been achieved.